High-intensity discharge (HID) Lamps include the groups of lamps commonly known as mercury vapour , metal halide, high and low pressure sodium, and xenon lamps.

High-intensity discharge (HID) Lamp produce light by striking an electrical arc within the lamp filled with a mixture of gas and metal

The main reason High-intensity discharge (HID) Lamps are used is the incredible amount of light that can come out of a moderatly sized lamp when comparing it to incandescent and flurescent alternatives. They are extremely common in areas where lots of light is required (eg street lighting, factories and sporting areas) or areas with access issues as they have a relitavely long service life.

There is an increase in the use of HID, especially Metal Halide lamps in the retail area including shopping centres, shop lighting and commercial buildings.

Most HID lamps require special starting and ignitor (control gear) to start the lamp. Many High-intensity discharge (HID) Lamps are nor compatible with each other so only use the lamp as specified by the light fittings manufacturer.